1. Field of the Invention
The present invention relates to improvement in a vehicle having an engine as a driving source and to a hybrid vehicle having two drive sources, i.e., an internal combustion engine and an electric motor.
2. Description of Background Art
An engine mounted on a vehicle is widely known. See, for example, JP-A No. 2002-295223, FIG. 3.
In FIG. 3 of JP-A No. 2002-295223, an engine as a power unit 1 (reference numerals from the publication are used hereinbelow) is provided with a crankshaft 9, a primary driven gear 12 attached to the crankshaft 9, a clutch mechanism 11 attached to the primary driven gear 12, a main shaft 13 attached to the clutch mechanism 11, a counter shaft 15 attached to the main shaft 13 via a main gear array 14 and a counter gear array 16, and an output sprocket 17 attached to the counter shaft 15.
The power of the crankshaft 9 is transmitted to the primary driven gear 12, the clutch mechanism 11, the main shaft 13, the main gear array 14, the counter gear array 16 and the counter shaft 15, and is outputted from the output sprocket 17.
In the meantime, as a means for applying a brake to a vehicle, a brake means and an engine brake are known. The engine brake, which utilizes a mechanical loss of the engine, reduces the number of revolutions of the engine and brakes a wheel utilizing a difference between the wheel and the revolution speed of the engine.
In the technique of JP-A No. 2002-295223, a case where the engine acts as an engine brake will be studied hereinbelow.
To brake a wheel, when a throttle valve is closed, the revolution speed of the engine is reduced, and the torque of the wheel is applied to the counter shaft 15. The torque of the wheel is transmitted to the counter gear array 16, the main gear array 14, the main shaft 13, the clutch mechanism 11, the primary driven gear 12 and the crankshaft 9, in this order. At this time, a braking force is applied to the wheel by a mechanical loss of the engine.
In the meantime, in recent years, a problem occurs with respect to the reduction in the fuel consumption. In an engine having a fuel injection system, when the engine acts as an engine brake, the fuel consumption is reduced by cutting the fuel. A technique for a further reduction of fuel consumption is preferable.
A power unit for a hybrid vehicle to be installed in a motorcycle is known as disclosed in JP-A No. 2006-044495.
According to the power unit for a hybrid vehicle as disclosed in JP-A No. 2006-044495, power from an internal combustion engine is transmitted to a rear wheel through a belt continuously variable transmission and a gear transmission constituting a power transmission mechanism. In addition, power from an electric motor is transmitted to the rear wheel through the gear transmission. The electric motor is disposed coaxially with a driven pulley constituting the continuously variable transmission, and is located lateral to the rear wheel.
However, according to this power unit, the electric motor is located rearwardly of and below a crankshaft of the internal combustion engine, and outwardly in the width direction of the driven pulley constituting the continuously variable transmission. The electric motor, disposed lateral to the rear wheel, has led to an increased lateral expansion. Also, the electric motor is heavy, and therefore, is preferably disposed in the vicinity of the center of a vehicle body.